The present invention relates to a glazed cement product and method for manufacturing thereof wherein the glazed cement product can be obtained by applying a glaze onto the surface of a molded body of cement, burning the glazed body and hydrating the burned body to harden, and improved in the strength of a molded body of cement by using, for example, prestressed concrete steel.
Hitherto, there was employed a method of laying reinforcing steel within a glazed cement product in order to increase the strength thereof. The product can be obtained by the following steps.
At first, a kneaded mixture of cement comprising cement, aggregate, water and the like is poured into a form wherein reinforcing steel is laid beforehand. Next, the resulting molded body of cement is hardened by curing in air for a prescribed time. Then a glaze is applied to the surface of the molded body of cement, the glazed product is burned at a prescribed temperature and then cooled in air. After such casting, the burned molded body of cement is hydrated to harden it thus manufacturing a hardened glazed cement product.
However, in case of manufacturing the above-mentioned conventional product, thermal stress is generated, while burning and cooling, by the difference in coefficients of thermal expansion between the reinforcing steel and the cementitious material causing cracks in portions of the cement material. For example, the coefficient of thermal expansion of reinforcing steel is about 17.3.times.10.sup.-6 .degree. C..sup.-1 and that of a molded body of cement is about 7 to 10.times.10.sup.-6 .degree. C..sup.-1 which, of course, varies depending on the types of aggregate used or mixing ratio of cement, aggregate and water. Accordingly the reinforcing steel expands about twice as much as a molded body of cement. As a result, the conventional product has problems because its strength is decreased rather than increased as would be expected of such a product containing reinforcing steel.
Accordingly, it is an object of the present invention to improve or remove the above-mentioned conventional drawbacks, and provide a glazed cement product wherein the generation of cracks is controlled and method for manufacturing such.